Many years ago (approximately 1970), I had a first generation microwave oven. One day my wife asked me to make some popcorn. I told her that I didn't want to get out the popcorn maker, clean it when I was done, etc.

She told me to put some popcorn in a paper bag and throw it in the microwave. I said "What?" She told me that they had these paper bags of popcorn at work. You put them the microwave oven. Obviously, this was what we now call microwave popcorn. But back then, no one had heard of it and you couldn't buy it yet in the grocery stores.

I decided to give it a try. But instead of using a paper bag, I took a CorningWare casserole dish (you know, the old white corning ware ceramic with the cornflower pattern on it -- maybe you are too young.)

I put some popcorn in, put the glass top on and put it in the microwave. I turned it on for a few minutes and nothing happened. I turned it on a little more and heard a few pops, maybe 10. I turned it on a little longer but nothing happened but I could see a little smoke.

I decided to take a look but there was a little steam/smoke coming off the lid. I am so glad that I grabbed a pot holder to take the lid off because when I touched the glass lid, the pot holder instantly caught on fire! Yes, the glass was that hot. In fact, the glass had melted! I had a stalactite of glass inside.

Well, the energy had to go somewhere. Popcorn is terrible at absorbing the microwaves. That is why the microwave popcorn you buy has so much oil in it. It is the oil that gets hot and makes the popcorn pop.

Well, glass, while a poor energy absorber, was better than the popcorn! People think that the glass won't take any of the energy but it will.

Bringing an old thread back to life, but what would happen if you had the popcorn in oil when you microwaved it?
I think I might try this with my old microwave before I throw it out. (Outside with a kill switch, of course)

No you can't buy microwave popcorn without oil (at least not in the stores). I haven't tried repeating the experiment with oil in the dish but it would probably work.

Yes there is a small amount of water inside the kernels but it is minimal and mostly bound into starch. It won't get hot enough. Try to pop popcorn at a low temperature (below 150 degrees C or 300 degrees F). You will find that the popcorn will not pop -- it has to get beyond a certain temperature for the pressure inside the kernel to build to the point where popping occurs.

For what it's worth, here is something I have been doing for more than 20 years with excellent results. Using a regular brown lunch bag like the kids take for school lunch, add 1/4 C. everyday popcorn like what you would use to pop in a pan with oil, fold the top once and secure with a single staple. Don't panic, that tiny bit of metal won't start a fire. Never has for me and my MW runs 1000 watts! But you can use scotch tape if it will make you feel better. Put it in the mw on high and listen for the popping to slow down. Pull it out. Don't wait for it to completely stop or you will have a lot of burned popcorn. Dump in a bowl and add what ever flavorings suit you or eat it plain from the bag.
ENJOY!

Another trick, if you don't want to use a staple or tape, is to just fold the top of the bag in half. Then in the center of the fold make two shallow rips (or cuts) about 1/4-in apart and 1/4-in deep. Take that mini-flap formed by the cuts and just fold it the other direction. Acts like a staple.

For years I have made popcorn this way: I put 1/4 cup of plain popcorn kernels (no oil) in a paper bag (lunch sack size), fold the top down two times with no staple or tape, put it in the microwave on the popcorn setting, listen for when it's done popping, take it out, drizzle 1 TBL of melted butter over it and sprinkle it with salt. It's perfect!